1. Field of the Invention
The present invention relates to a setting tool for driving nail-shaped fastening elements into hard constructional components and including a guide cylinder, a drive piston axially displaceable in the guide cylinder, a guide housing a slide displaceable in the guide housing and having a pawl cooperating with a stop surface provided on the drive piston and pivotable out of an axial projection of the drive piston against a biasing force applied by a spring member, and an operating cam cooperating with a control profile provided on the pawl.
2. Description of the Prior Art
For driving nail-shaped fastening components into hard constructional components such as concrete, stone, or steel and the like, setting tools, which are operated by high-pressure gases, are used. In widely used and preferred, from the standpoint of safety, setting tools, the high-pressure gases act on a drive piston which, in turn, drives a to-be-driven fastening element into a hard constructional component. While these tools have significant advantages, they also have a serious drawback which consists in that the drive piston should be pushed back in its initial position after each drive-in process.
German Patent no. 2,026,293 discloses an explosive powder charge-operated setting tool in which the drive piston is returned to its initial position after each setting process manually. In this setting tool, a slide is displaced in a guide housing with a handle accessible from outside of the setting tool. A tension spring connects the slide with a front, in a setting direction, region of the guide housing. The slide includes a pawl pivotable into the axial projection of the drive piston by a spring member when the slide is displaceable with the handle in a direction opposite to the setting direction. When the slide is in its initial position, a control profile provided on the pawl cooperates with an operating cam which retains the pawl from projecting into the axial projection of the drive piston.
This type of returning of the drive piston into its initial position is very cumbersome and can be dangerous when simultaneously with the displacement of the slide with the handle in a direction opposite to the setting direction, a new cartridge is ignited.
Accordingly, an object of the present invention is a high-pressure gas-operated setting tool in which the drive piston automatically returns to its initial position after each setting process.